Tapping arrangement for doubleflow low-pressure turbine



March 15, 1949. c. c. FRANCK ETAL 2,464,388

TAPPING ARRANGEMENT FOR DOUBLE-FLOW LOW-PRESSURE TURBINE Filed Oct. 25, 1947 INVENTORS CLARENCE. C. FRANCK, Em: Azizr-i'mmulsr QIJYDIM ATTORNH Patented Mar. 15, 1949 TAPPING ARRANGEMENT FOR DOUBLE- FLOW LOW-PRESSURE TURBINE Clarence C. Franck, Swarthmore, and Eric A. Zetterquist, Drexel Hill, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 23, 1947, Serial No. 781,570

2 Claims.

1 The invention relates to a tandem steam turbine plant wherein a single-flow, high-pressure unit exhausts to a double-flow, low-pressure unit having oppositely directed bladed flow paths between the inlet and the condenser connections and it has for itsobject to provide the flow paths with blading such that a single bleeder connection may be made to each flow path at different pressure points along the paths without involving more than a relatively smallchange in steam thrust brought about by closing either connection.

Present 3600 tandem units with a double-flow exhaust and high initial pressure are arranged for a carry-over pressure of about 40 to 50 pounds absolute. This eliminates the need for more than one feed-water heater taking steam from the double-flow low-pressure blading, but it necessitates, for mechanical reasons, a relatively lbw pressure in the impulse chamber of the highpressure element, which results in loss of chiciency, particularly at lighter loads. For the sake of efliciency, it also becomes necessary to use a step-up drum and a two-step dummy, the high-pressure section of which, at least, must be made integral with the cylinder and is, therefore, subject to distortions.

In accordance with our invention, there is provided a tandem arrangement wherein the carryover pressure is around 100 pounds absolute, thereby enabling the use of a high-pressure element similar to a superposed unit with a single step, separate dummy, constant thrust diameter type of reaction blading and higher impulse chamber pressure with resulting higher over-all emciencies, such a unit being more particularly disclosed and claimed in the patent to Zetterquist, No. 2,300,758, granted November 3, 1942.

' nection to'each flow path, closing of either bleeder connection results only in a relatively small change in thrust on the unit, this result being accomplished by providing each flow path with exhaust blading of equal dimensions preceded by constant thrust diameter blading with one bleeder connection made between the exhaust 2 blading and the constant thrust diameter blades at one side and the other bleeder connection being made along the constant thrust diameter blading at the other side.

The foregoing and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. l is a view, partly in elevation and partly in section, showing a tandem compound turbine with the improvement incorporated in the doublefiow, low pressure unit; and

Fig. 2 is a fragmentary sectional view showing the steam path and blading therein of the lowpressure unit.

In the drawing, there is shown a tandem tur-' bine arrangement including a high-pressure turbine element 10 joined by a cross-over connec tion communicating with the inlet l2 of the double-flow, low pressure unit M. The inlet 12 is connected by oppositely directed flow paths f5 and Hi to exhaust chambers 11, communicating with a condenser (not shown).

As already pointed out, the high-pressure unit is preferably of the type disclosed and claimed in Patent No. 2,300,758 aforesaid, the characteristic features thereof being the constant thrust diameter blades, enabling the use of a dummy of single diameter. By the use of such a unit, higher inlet and exhaust pressures may be employed without excessive end thrust while at the same time providing for a higher pressure at the inlet of the double-flow unit. If, with this arrangement, a conventional double-flow unit were used with bleeder connections for a pair of feed-water heaters, it would be necessary to connect each connection with both flow paths to avoid excessive end thrust in the event of closing down either heater.

To enable the pair of heaters to be connected at suitable points along their respective flow paths involves the arrangement of blading in the latter and to be immediately described.

As shown, each of the flow paths is and it of the low-pressure unit contains constant thrust diameter blading l9 and 20 adjacent to the inlet I! followed by exhaust blading 2i and 2.2 discharging to the exhaust chambers l1, IT. The groups of exhaust blading 2| and 22 of the flow paths have the same physical dimensions, in consequence of which the pressures at the inlets thereof are approximately the same and the thrust of one approximately balances that of the other.

The blade groups 19 and 20 have blading o! the same constant thrust diameter.

Steam is discharged from the flow path l6 through a passage or passages 24 to a chamber 25 supplying a low-pressure heater (not shown) and steam is discharged from the flow path l through a passage or passages 26 to a turbine chamber 21 supplying a high-pressure heater (not shown). The passage or passages 24 communicate with the flow path between the constant thrust diameter blading 20 and the exhaust blading 22, whereas the passage or passages 28 communicate with the flow path at a suitable interstage point of the constant thrust diameter blading 19.

For normal operation, the quantity of steam extracted for the heaters is approximately the same. Hence, as shown with the same physical dimensions of the two groups of exhaust blading, the pressures before their inlets become approximately the same and there is an approximate balance of thrust. Should, with this arrangement, the first heater supplied from the connection 24 be taken out of service, the pressure before the exhaust blading 22 would rise, say 10 per cent. from 10 pounds to 11 pounds. Taking the constant thrust diameter for the first groups and the average thrust diameter of the exhaust groups as shown, the unbalance of thrust becomes, with a 44-inch constant thrust diameter and a 56-inch average thrust diameter,

1 x (56 -44 =1150 pounds which is about 4 per cent of the total thrust that may be taken on the thrust bearing and hence is of little consequence. With the heater supplied from the connection 26 shut off, the unbalance would be about the same.

ing an inlet joined by oppositely directed flow paths to condenser exhaust chambers, a constant thrust diameter blade group and an exhaust blade group in each flow path with the exhaust blade groups having like physical dimensions, and a bleeder connection communicating with each flow path ahead of the exhaust blade group thereof, said bleeder connections being positioned along the flow paths so that more stages of constant thrust diameter blading are interposed between one connectlon and the inlet than between the other connection and the inlet.

2. Apparatus as claimed in claim 1 wherein one bleeder connection communicates with its flow path between the exhaust blade group and the constant thrust diameter blade group and the other bleeder communication communicating with its flow path at an interstage point along the constant thrust diameter blade group.

3. Turbine apparatus substantially as herein described with reference to the accompanying drawings.

CLARENCE C. FRANCK. ERIC A. ZETTERQUIST.

No references cited.

Certificate of Correction Patent No. 2,464,388. March 15, 1949.

v CLARENCE C. FRANCK ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 32, beginning with 3. Turbine apparatus strike out all to and including the Word and period drawings, line 34, comprising claim 3; and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 6th day of September, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommz'asioner of Patents. 

